Sea sponges evolving super-fast to cope with warming waters
While the marine heatwave has killed hundreds of thousands of sea sponges in New Zealand, those that have survived have developed incredible resilience. Credits: Image - Supplied; Video - Newshub Sea sponges are showing evidence of super-fast evolution to cope with waters warming up because of climate change. While the marine heatwave has killed hundreds of thousands of sea sponges in New Zealand, those that have survived have developed incredible resilience. The colourful creatures are a critical part of the ocean's food chain, but consecutive marine heatwaves have been bleaching and killing millions of them around the world, which Victoria University marine biologist James Bell says is a big loss. "If we lose the sponges then we lose the habitat which all those other organisms are associated with - and it potentially affects the food we get on our table," Bell said. So scientists at Victoria University investigated how the common sponge, the Crella incrustans, reacted to marine heatwave conditions in the lab. They put the sponges, gathered from Wellington Harbour, into tanks of 21C and noticed an increase in harmful pathogenic and stress-associated bacteria and a decrease in their normal symbiotic bacteria - tiny organisms that live inside the sponges. After just 10 days, a third of the sponges died, however the survivors bred more resilient babies who could tolerate warmer waters. "They didn't have any of the nasty bacteria living within them, that's probably one of the reasons why they survived. It's really exciting because it opens the possibility that sponges may survive in the future," Bell said. Bell worked alongside PhD student Francesca Strano for her thesis. "They showed a lot of mortality, but the ones that survived, they were doing really well - so this is good." Although Strano said more research is needed. "It's possible sponges losing some of their microbes could be a good thing, enabling them to 'shuffle' or 'switch' the microbes they contain to get new ones and provide the potential for them to survive in new or different conditions," she said. "However, during this process they could also lose some microbes that are important for other functions - for example, detoxification." The researchers want to apply the marine heatwave experiments to other sea sponges in New Zealand and around the world. "There are something like 800 species in New Zealand, so we want to understand if this process is also the same for other species," said Bell. In an effort to save as many sponges as they can from climate change.